Method of manufacturing plate heat exchanger and plate heat exchanger

ABSTRACT

In a plate heat exchanger, it is aimed to enhance strength, such as the pressure resistance and the internal pressure fatigue resistance, by increasing the joint area of a joint portion joined by brazing in a wave-patterned portion. Before a brazing process of the plate heat exchanger, a plurality of plates are stacked and pressure is applied thereto. By this pressure process, indentations of approximately “0.05 mm to 0.1 mm” are formed at contact points  9  of wave patterns in adjoining lower and upper plates. By brazing the plates after this pressure process, the joint area of the joint portion joined by brazing is increased. The increased joint area enhances the joint strength, and thus the strength of the plate heat exchanger such as the pressure resistance and the internal pressure fatigue resistance can be enhanced.

TECHNICAL FIELD

This invention relates to a method of manufacturing a plate heat exchanger and a plate heat exchanger.

BACKGROUND ART

A plate heat exchanger includes stacked plates, in each of which a plurality of wave patterns are formed on each heat-transfer surface in order to provide flow passages for a heating medium and a cooling medium (also called a refrigerant). The plates are configured such that part of crest portions of the wave patterns in one of two adjoining plates are in contact with part of trough portions of the wave patterns in the other plate. These contact portions are joined by brazing, and such joint portions are formed over the entire area of each plate, thereby maintaining strength.

On the other hand, near each inlet and outlet of the heating medium and the cooling medium provided in each plate, there is an area where no joint portion of the wave patterns described above can be created because of the need to completely separate the heating medium and the cooling medium. Because of this area, strength is reduced near each inlet and outlet compared to the other area.

Thus, in some conventional heat exchangers, joint portions are formed near each inlet and outlet by making part of the ridge lines of the wave patterns meander or bend (e.g., Patent Literature 1).

Patent Literature

-   Patent Literature 1: JP 7-243781 A

DISCLOSURE OF INVENTION Technical Problem

However, in a configuration where part of the ridge lines of the wave patterns is made to meander or bend, there have been problems. The problems include increased susceptibility to fractures at the time of molding and decreased accuracy in size after molding, due to unevenness of stretch at meandered or bent portions of the plates at the time of molding. It has also been a problem that the cost of manufacture of molds for molding the plates is increased due to complexity of the wave patterns.

In this invention, indentations having a depth of 0.05 mm to 0.1 mm are formed at joint portions of wave patterns provided in each plate by applying pressure to a plurality of stacked plates before brazing, in order to increase the contact area between wave patterns to be joined. By performing brazing in this state, the area of joint portions joined by brazing is increased. It is aimed to provide a method of manufacturing a plate heat exchanger with excellent reliability in molding the plates, by using a mold that has increased strength and requires no complex processing because of this increased joint area.

Solution to Problem

In a method of manufacturing a plate heat exchanger according to this invention, the plate heat exchanger includes a plurality of plates stacked and configured in a rectangular shape having a long side and a short side, each of the plurality of plates having formed therein a wave pattern waving in a stacking direction, wherein

when one side of the stacking direction is defined as a lower side and an other side is defined as an upper side, a lower side plate and an upper side plate adjacent to each other have between them a plurality of intersecting portions at intersections of a plurality of bottom ridge lines representing a bottom of a wave of the upper side plate and a plurality of top ridge lines representing a top of a wave of the lower side plate, and the bottom of the wave of the upper side plate and the top of the wave of the lower side plate are joined by a brazing process at the plurality of intersecting portions, and

the method of manufacturing the plate heat exchanger includes:

a pressure process of forming indentations on the bottom of the wave of the upper side plate and the top of the wave of the lower side plate at least at some of the plurality of intersecting portions by stacking the plurality of plates before the brazing process in a same order as in a completed state and applying pressure thereto in the stacking direction to compress the plurality of stacked plates.

Advantageous Effects of Invention

This invention can provide a plate heat exchanger to be joined by brazing that is easy to manufacture and offers enhanced pressure resistance performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a plate heat exchanger 100 according to a first embodiment.

FIG. 2 is a cross sectional view of a conventional plate heat exchanger corresponding to the cross section A-A of FIG. 1.

FIG. 3 is a view corresponding to a cross sectional view taken on the line A-A of the plate heat exchanger 100 of the first embodiment (before applying pressure).

FIG. 4 is a view showing a pressure process of the first embodiment.

FIG. 5 is a view showing FIG. 3 after applying pressure.

FIG. 6 is a plan view of the plate heat exchanger 100 of a second embodiment.

FIG. 7 is a cross sectional view taken on the line B-B of the plate heat exchanger 100 of the second embodiment before applying pressure.

FIG. 8 is a cross sectional view taken on the line B-B of the plate heat exchanger 100 of the second embodiment after applying pressure.

DESCRIPTION OF EMBODIMENTS Embodiment 1

Referring to FIGS. 1 to 5, a method of manufacturing a plate heat exchanger 100 according to a first embodiment will be described.

FIG. 1 is a plan view of the plate heat exchanger 100. The configuration of the plate heat exchanger 100 is approximately the same as that of a conventional plate heat exchanger. The difference from the conventional plate heat exchanger lies in that a height difference of “0.05 mm to 0.1 mm” is provided in the height of wave patterns, as shown in FIG. 3 to be described later, and this height difference is offset by a pressure process to be described later in order to enlarge brazing portions between crest portions and trough portions on adjoining plates.

(Configuration of the Plate Heat Exchanger 100)

The plate heat exchanger 100 includes a plurality of plates stacked and configured in a rectangular shape having long sides 102 a and 102 b and short sides 101 a and 101 b. In each of the plurality of plates, wave patterns waving in a stacking direction are formed. In the plate heat exchanger 100, when one side of the stacking direction is defined as a lower side and the other side is defined as an upper side, a lower side plate and an upper side plate adjacent to each other have between them a plurality of intersecting portions 105 at intersections of a plurality of bottom ridge lines 106 representing the bottom of the wave of the upper side plate and a plurality of top ridge lines 107 representing the top of the wave of the lower side plate. Then, the bottom of the wave of the upper side plate and the top of the wave of the lower side plate are joined by a brazing process at the plurality of the intersecting portions 105.

In each plate of the plate heat exchanger 100, near one short side 101 a, a cooling medium inlet 111 (an opening) for passing a cooling medium and a heating medium outlet 112 (an opening) for passing a heating medium for heat exchange with the cooling medium are formed across the short side. Near the other short side 101 b, a cooling medium outlet 113 (an opening) for passing the cooling medium and a heating medium inlet 114 (an opening) for passing the heating medium are formed across the short side. The wave patterns are formed in an area between a pair of the cooling medium inlet 111 and the heating medium outlet 112 and a pair of the cooling medium outlet 113 and the heating medium inlet 114.

The configuration of the plate heat exchanger 100 described so far is the same as that of the conventional plate heat exchanger.

FIG. 2 is a cross sectional view of the conventional plate heat exchanger corresponding to the cross section A-A of FIG. 1.

(Cross Section of the Conventional Plate Heat Exchanger)

The cross section of FIG. 2 shows the plurality of plates stacked in a stacking direction 104. In two adjoining lower and upper plates 1 and 2, crest portions 3 (top) of the wave patterns formed in one of the plates are in contact with trough portions 4 (bottom) of the wave patterns formed in the other plate at contact points 5. The cross section of the crest portions 3 or the trough portions 4 of the wave patterns formed in the plates 1 and 2 is shaped in an approximately circular arc. Further, the ridge lines of the respective wave patterns of the plates 1 and 2 are formed in mutually intersecting directions, so that the contact points 5 (corresponding to intersecting portions) between the two plates are in point contact.

(Characteristic of the Plates of the Plate Heat Exchanger 100)

FIG. 3 shows a cross section of the plate heat exchanger 100 corresponding to the cross section A-A of FIG. 1 before the “pressure process” to be described later. For the purpose of explanation, FIG. 3 shows both the areas 6 a and 6 b and the area other than the areas 6 a and 6 b. Thus, FIG. 3 does not show the actual cross section A-A. The plates of the plate heat exchanger 100 are characterized in that, as shown in FIG. 3, a wave height H1 of the wave patterns in the area 6 a near the cooling medium inlet 111 and the heating medium outlet 112 (area near the openings) and the area 6 b near the cooling medium outlet 113 and the heating medium inlet 114 (area near the openings) is higher (longer) by a “size a” compared to a wave height H2 of the wave patterns in the other area (area other than the areas 6 a and 6 b).

Here, the “size a” is defined as follows:

0.05 mm≦a≦0.1 mm

As described above, each plate is characterized in that a bottom position 121 of the wave in a direction from the upper side to the lower side of the stacking direction 104 in the areas 6 a and 6 b is lower by the “size a” than a bottom position 122 of the wave in the area other than the areas 6 a and 6 b.

The plate 1 (lower side plate) and the plate 2 (upper side plate) are manufactured by press molding. The above range “0.05 mm to 0.1 mm” of the “size a” can be realized by press molding the plates 1 and 2 in a mold for molding the plates 1 and 2 configured to produce a difference corresponding to “0.05 mm to 0.1 mm” in the height of a place where the wave patterns are molded.

The plates 1 and 2 are configured as described above. Thus, referring to FIG. 3, when a plurality of the plates 1 and 2 are stacked before being brazed as shown in FIG. 1, between two adjoining lower and upper plates 1 and 2, the crest portions of the wave patterns provided in one of the plates are in point contact with the trough portions of the wave patterns of the other plate at contact points 9 in the areas 6 a and 6 b near each inlet and outlet. On the other hand, wave-patterned portions in the other area have gaps 10 of 0.05 mm to 0.1 mm between the two plates.

Referring to the plate 2-1 in FIG. 3, although the bottom position 121 of the wave in the areas 6 a and 6 b is lower by the “size a” compared to the area other than the areas 6 a and 6 b, this is an example. In the plate 2-1 (and in other plates as well), the top position of the wave at the upper side may be higher by the “size a” in an upward direction in the areas 6 a and 6 b.

(Pressure Process)

FIG. 4 is a view showing the pressure process.

FIG. 5 shows a state of FIG. 3 after the pressure process.

Before the brazing process, a required number of the plates 1 and 2 are stacked, and, as shown in FIG. 4, pressure is applied to approximately the entire area of the plates 1 and 2 by using pressure jigs 16 a and 16 b having a flat surface, while maintaining the parallel positions of the lower and upper surfaces. As shown in FIG. 5, this pressure process causes plastic deformation at the contact points 9 (contact points between the top and the bottom) of the wave patterns in the areas 6 a and 6 b near each inlet and outlet. As a result, indentations 11 are formed at the contact points 9 on both of the adjoining lower and upper plates, so that the contact state changes to area contact from point contact of before applying pressure.

In this way, before the brazing process, a plurality of the plates are stacked in the same order as in a completed state. Then, by applying pressure in the stacking direction to compress the plurality of the stacked plates, indentations are formed on the bottom of the wave of the upper side plate and the top of the wave of the lower side plate at least at some of a plurality of the contact points (intersecting portions).

(Depth of Indentations)

At this time, the depth of the indentations 11 formed by applying pressure should be a depth that approximately offsets the “size a” (0.05 mm to 0.1 mm), i.e., a predetermined difference between the wave height of the wave patterns in the areas 6 a and 6 b near each inlet and outlet and the wave height of the wave patterns in the other area. This is approximately enough to close the gaps 10 in the area not near each inlet and outlet. Also, by configuring a “size 6 a-w” and a “size 6 b-w” of the areas 6 a and 6 b near each inlet and outlet to be 5 to 50 mm from the edge of each inlet and outlet, power required for applying pressure by the pressure jigs 16 a and 16 b can be reduced.

By stacking the plates 1 and 2 and then applying pressure as described above, the plates are configured to have the indentations 11 to make them fit together. In this state, the plates are taken out of the pressure jigs 16 a and 16 b to relieve the applied pressure. Then, the plates are brazed by furnace brazing or the like, without changing the stacked order at the time of applying pressure.

As presented above, the plate heat exchanger 100 is configured such that, in the wave patterns formed in each plate, the wave height of the wave patterns near each inlet and outlet of the heating medium and the cooling medium is higher by “0.05 mm to 0.1 mm” than the wave height of the wave patterns in the other area, in order to increase the area of joint portions joined by a brazing material in the wave patterns near each inlet and outlet of the heating medium and the cooling medium compared to the area of joint portions joined by the brazing material in the other area. Then, before brazing, a predetermined number of these plates are stacked and pressure is applied to the stacked plates by using the pressure jigs. Brazing is performed after this pressure process has formed indentations approximately enough to offset the difference in the height of the wave patterns.

Thus, because of the indentations 11, area contact occurs at the contact points 9 in the areas 6 a and 6 b near each inlet and outlet. As a result, due to the brazing material that wetly spreads around the contact points 9 by brazing, the joint strength in the areas 6 a and 6 b near each inlet and outlet is increased, so that the strength of the plate heat exchanger such as the pressure resistance and the internal pressure fatigue resistance can be increased and quality can be improved. At the time of furnace brazing, other internal parts of the plate heat exchanger to be joined with the plates 1 and 2 can be assembled and brazed together with the plates.

Further, since there are no meandering portions, bending portions, or the like, the molds for molding the plates can be manufactured inexpensively. Also, in the molding of the plates, the cost of manufacture can be reduced because fracture failures are less likely to occur, and so on.

Embodiment 2

Next, referring to FIGS. 6 to 8, a method of manufacturing the plate heat exchanger 100 according to a second embodiment will be described. In the first embodiment described above, the indentations 11 are formed near each inlet and outlet by applying pressure, in order to increase the area joined by brazing and enhance the joint strength. The second embodiment will describe a case in which the strength is enhanced over the entire area of the plates.

FIG. 6 is a schematic view of the plate heat exchanger 100 according to the second embodiment.

FIG. 7 is a view showing the cross section B-B of FIG. 6 of a plurality of stacked plates before applying pressure.

FIG. 8 is a view showing the cross section B-B of FIG. 6 of the plurality of stacked plates after applying pressure.

In FIGS. 6 and 7, a wave height 13 of the wave patterns formed in the plates 1 and 2 is ideally approximately uniform over an entire area 12 of the plates. In actuality, however, the wave height 13 includes variations occurring when the plates 1 and 2 are press molded. This causes gaps 14 at contact portions of adjoining wave patterns at places where the wave height 13 is relatively low. Performing brazing in this state tends to reduce the area of joint portions joined by the brazing material at contact portions of the wave patterns where gaps exist. This state occurs at a large number of arbitrary places over the entire area 12 of the plates 1 and 2. At these places, variations occur in the area of joint portions joined by the brazing material, causing variations in the strength of the plate heat exchanger.

(Pressure Process)

To solve the above problem, a required number of the plates 1 and 2 are stacked before being brazed. Then, as with the first embodiment as shown in FIG. 4, pressure is applied to approximately the entire area of the plates 1 and 2 by using the pressure jigs 16 a and 16 b having a flat surface, while maintaining the parallel positions of the lower and upper surfaces. This causes plastic deformation at the contact portions of the wave patterns over approximately the entire area. As a result, indentations 15 are formed at the contact portions in both of adjoining lower and upper plates, so that the contact state changes to area contact from point contact of before applying pressure. Also, by configuring the depth of the indentations 15 formed by applying pressure such that the depth approximately offsets the gaps 14 caused by variations in the wave height 13, the gaps 14 are closed. The appropriate depth of the indentations 15 in this case is “0.05 mm to 0.1 mm”, considering the level of variations in the wave height 13 caused by press molding.

In this way, before the brazing process, a plurality of the plates are stacked in the same order as in the completed state. Then, by applying pressure in the stacking direction to compress the plurality of the stacked plates, indentations are formed on the bottom of the wave of the upper side plate and the top of the wave of the lower side plate at least at some of a plurality of the contact points (intersecting portions).

By stacking the plates 1 and 2 and then applying pressure as described above, the plates are configured to have indentations 15 to make them fit together. In this state, the plates are taken out of the pressure jigs 16 a and 16 b to relieve the applied pressure. Then, the plates are brazed by furnace brazing or the like, without changing the stacked order at the time of applying pressure. In this way, the area of joint portions joined by the brazing material can be increased over approximately the entire area of the plate heat exchanger.

Further, by configuring the gaps 14 caused by variations in the wave height 13 to be closed by applying pressure with the pressure jigs 16 a and 16 b, variations in the area of joint portions can also be decreased. Thus the joint strength can be increased, and variations in the joint strength can also be decreased, thereby leading to consistency and enhancement of the quality of the plate heat exchanger in terms of strength.

At the time of furnace brazing, other internal parts of the plate heat exchanger to be joined with the plates 1 and 2 by brazing can be assembled with the plates 1 and 2 and brazed together.

REFERENCE SIGNS LIST

-   1: plate, 2: plate, 3: crest portions of the wave patterns, 4:     trough portions of the wave patterns, 5: contact points, 6 a, 6 b:     areas near each inlet and outlet, 7: wave height, 8: wave height, 9:     contact points, 10: gaps, 11: indentations, 12: entire area of the     plate, 13: wave height of the wave patterns, 14: gaps, 15:     indentations, 16 a, 16 b: pressure jigs, 100: plate heat exchanger,     101: short sides, 102: long sides, 104: stacking direction, 105:     intersecting portions, 106: bottom ridge lines, 107: top ridge     lines, 111: cooling medium inlet, 112: heating medium outlet, 113:     cooling medium outlet, 114: heating medium inlet, 121, 122: bottom     positions 

1. A method of manufacturing a plate heat exchanger, the plate heat exchanger including a plurality of plates stacked and configured in a rectangular shape having a long side and a short side, each of the plurality of plates having formed therein a wave pattern waving in a stacking direction, wherein when one side of the stacking direction is defined as a lower side and an other side is defined as an upper side, a lower side plate and an upper side plate adjacent to each other have between them a plurality of intersecting portions at intersections of a plurality of bottom ridge lines representing a bottom of a wave of the upper side plate and a plurality of top ridge lines representing a top of a wave of the lower side plate, and the bottom of the wave of the upper side plate and the top of the wave of the lower side plate are joined by a brazing process at the plurality of intersecting portions, the method of manufacturing the plate heat exchanger, comprising: a pressure process of forming indentations on the bottom of the wave of the upper side plate and the top of the wave of the lower side plate at least at some of the plurality of intersecting portions by stacking the plurality of plates before the brazing process in a same order as in a completed state and applying pressure thereto in the stacking direction to compress the plurality of stacked plates.
 2. The method of manufacturing the plate heat exchanger of claim 1, wherein each plate of the plurality of plates has formed therein, near each of the short side at both ends, two openings arranged side by side across the short side, and the each plate also has formed therein the wave pattern between both pairs of the two openings respectively formed near the each of the short side at both ends, and, in the wave pattern on the each plate of the plurality of plates, a distance H1 of the stacking direction between the bottom of the wave and the top of the wave of the wave pattern in an area near the openings, which is an area near each of the two pairs of the two openings, is longer by a “size a” than a distance H2 of the stacking direction between the bottom of the wave and the top of the wave of the wave pattern in an area other than the area near the openings, and the pressure process forms the indentations that approximately offset the “size a”.
 3. The method of manufacturing the plate heat exchanger of claim 2, wherein in the each plate, a bottom position of the wave in a direction from the upper side to the lower side of the stacking direction in the area near the openings is lower by the “size a” toward the lower side than a bottom position of the wave in the direction from the upper side to the lower side of the stacking direction in the area other than the area near the openings.
 4. The method of manufacturing the plate heat exchanger of claim 2, wherein in the each plate, a top position of the wave in a direction from the lower side to the upper side of the stacking direction in the area near the openings is higher by the “size a” toward the upper side than a top position of the wave in the direction from the lower side to the upper side of the stacking direction in the area other than the area near the openings.
 5. The method of manufacturing the plate heat exchanger of claim 2, wherein the “size a” is 0.05 mm≦a≦0.1 mm.
 6. A plate heat exchanger including a plurality of plates stacked and configured in a rectangular shape having a long side and a short side, each of the plurality of plates having formed therein a wave pattern waving in a stacking direction, wherein when one side of the stacking direction is defined as a lower side and an other side is defined as an upper side, a lower side plate and an upper side plate adjacent to each other have between them a plurality of intersecting portions at intersections of a plurality of bottom ridge lines representing a bottom of a wave of the upper side plate and a plurality of top ridge lines representing a top of a wave of the lower side plate, and the bottom of the wave of the upper side plate and the top of the wave of the lower side plate are joined at the plurality of intersecting portions, and wherein indentations are formed on the bottom of the wave of the upper side plate and the top of the wave of the lower side plate at least at some of the plurality of intersecting portions. 